Signal translating apparatus



Dec. 28, 1937. E. c. GUEDON SIGNAL TRANSLATING APPARATUS Filed Nov. 12, 1936 Patented Dec. 28, 1937 2,103,3fii

rarest" creme SIGNAL TRANSLATING APPARATUS Emile C. Guedon, Audubon, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 12, 1936, Serial No. 110,436

6 Claims.

This invention relates to signal translating apparatus of the type employed in electrical phonograph sound recording and reproducing systems, and more particularly to a mounting for the vibratable armature thereof, my present invention being an improvement upon that disclosed in my U. S. Patent No. 1,995,177, and upon that disclosed in U. S. Patent No. 1,783,044, issued to E. W. Kellogg.

In such signal translating devices of the electromagnetic type, the armature is mounted to vibrate between a pair of associated pole pieces either in response to variations in contour of the recorded groove, as in the reproduction of a record, or in response to signal currents flowing in one or more coils associated with eitherthe armature or the pole pieces, as during the recording of a selection. The armature normally stands midway between the pole pieces in its unexcited condition, but during operation of the device, the armature is deflected from its central position either by the mechanical force exerted thereonloy the record groove, or by forces derived from electric currents flowing in the coil or coils, as the case may be.

In recent years, considerable advance has been made in the art of recording sound, and it is now possible to record frequencies up to the order of 10,006 cycles. Obviously, if these high fidelity records are to be reproduced with any degree' of faithfulness, it is necessary not only that the reproducing needle follow the groove variations accurately, but also that the armature of the sound translating device accurately generate voltages corresponding'to the sound being reproduced. This necessitates an armature which has a small mass and a low moment of inertia about its vibratory axis because of the relatively slightpower obtainable from the sound groove.

In the constructions disclosed in the aforementioned patents, the armature pivot shaft is encased in a sleeve of rubber or other resilient material suitably held in a bearing groove or channel, the rubber sleeve serving as a substantially frictionless bearing and, at least in part, to center the armature between the pole pieces. I have found, however, that while this construction is quite satisfactory for reproduction of the lower frequencies, there is, nevertheless, suf- (Cl. Nil-400.41)

lating device which isfree from the foregoing objection.

More specifically, it is an object of my present invention to provide an improved signal translating device which is capable of accurately reproducing frequencies within the full range now capable of being recorded.

Another object, of my present invention is to provide an improved signal translating device as aforesaid in which the frictional resistance offered to the vibration of the armature is reduced to a minimum.

A further object of my present invention is to provide an improved signal translating device in which the frictional resistance offered to the vibration of the armature may be easily and readily adjusted.

It is also an object of my present inventionto provide an improved signal translating device as aforesaid which is compact, simple and practical in construction, which can be readily assembled and adjusted for proper operation, and which is highly efficient in use.

In accordance with my present invention, I eliminate the rubber bearing sleeve from the armature pivot shaft, and mount it between two pivct bearings, one at each end, having a minimum bearing contact With'said shaft consistent with satisfactory operation of the device. One of the pivot bearings is preferably fixed, and the other one is made adjustable whereby the bearing friction may be adjusted to suit various conditions of use. Preferably, also, at least one of the pivot bearings is made hollow in order to permit entry of the needle screw to permit clamping the needle in place.

The novel features that I considercharacten istic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with additional objects and advantages thereof, will best be un derstood from the following description of several embodiments thereof when read in connec- I wherein similar reference characters designate corresponding parts throughout, there is shown, in Fig. 1, a molded insulating base I on which is mounted a metallic frame 3 having a pair of pole pieces 5 (only one of which is shown in the drawing) secured thereto in spaced relation to each other to provide an air gap. A permanent magnet l, firmly pressed against the pole pieces 5 by a spring 9, serves to supply a flux to the pole pieces 5, while a casing member ll serves to enclose the structure heretofore described as well as that presently to be described.

Secured to the bottom of the frame 3 is a U- shaped bracket l3 having the upstanding arms l5 and I! to the former of which is staked or otherwise suitably secured a hollow bearing member l 9 and in the latter of which is screw threaded a conical bearing member 2|, the bearing 2i being locked in any desired position of adjustment by a nut 23. The bearing members I9 and 2| are received within the hollowed ends of the pivot shaft 25 of an armature 2? whereby the armature is mounted for vibratory movement between the pole pieces 5, a spring 28, which connects the shaft 25 with the frame 3, serving to normally maintain the armature 2T properly centered in the air gap between the pole pieces 5. This arrangement provides only edge contact between the ends of the pivot shaft 25 and the bearings l9 and 2i, as represented by the dotted line 29, for example, whereby a minimum frictional resistance is offered to vibratory movement of the armature 25, and the bearing 21 may be adjusted to provide the desired friction in accordance with the conditions under which the device is to be used. A winding or coil 3|, provided with terminal leads 33 which are connected to output terminals 35 embedded in the base I for external connection to a suitable electrical amplifying circuit (not shown), surrounds the armature 2'! and may either have varying voltages set up therein in response to vibration of the armature 27 under the influence of a record, as during reproduction, or may cause the armature 21 to vibrate in response to signal currents flowing therein, as during recording. The bearing member 19 is preferably made hollow for the reception of a needle screw 35 for securing a needle 3'! in the socket 39 of the armature 21, and the pivot shaft 25 is made hollow not only to receive the bearings l9 and 2| with minimum contact therewith, but also to reduce the mass of the armature, 7

and thereby its moment of inertia about its vibratory axis.

In the modification of my invention shown in Fig. 2, the pivot shaft 25 is also made hollow and at one end is provided with a plate 45 having a conical recess or seat which receives a solid conical bearing 4| corresponding to the bearing 2| of Fig. l but fixed to the arm [1. The other end of the shaft 25 is conically tapered, as at 43, and is received by a hollow bearing sleeve 45 which is internally also conically tapered. Thus, the end @3 of the shaft 25 of this modification of my invention also has only edge contact with its as sociated bearing sleeve 45, while the plate 40 has substantially point contact with the bearing member 4|. The bearing sleeve 45 may be made adjustable on the arm [5 axially of the shaft 25 and locked in adjusted position by a set screw 4'! which is threaded into the arm l5.

The modification of my invention shown in Fig. 3 is similar to that shown in Fig. 2, but the plate 46 is omitted and in place of the conical bearing 4|, a ball bearing 41 may be employed against the hollow end of the pivot shaft 25 to provide edge engagement with the open end thereof, similarly to the construction of Fig. 1. If desired, the plate 4!] may, of course, be retained and the ball bearing 41 engaged with the conical recess therein, whereby an edge or line contact similar to the contact 29 is obtained.

Although I have shown and described several specific embodiments of my present invention, I

am fully aware that many modifications thereof are possible. For example, the bearing members I5, 2|, 4|, 45, and 41 need not necessarily be conical or spherical, but may be suitably tapered along any other curves or contours to provide edge or line contact with the hollow ends of the pivot shaft 25. Other changes of a similar nature may also be made, and I therefore desire that my invention shall not be limited except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In an electric signal translating device, the combination of an armature including a pivot shaft hollowed out at its ends and having a socket therein for the reception of a needle, and a pair of tapered bearing members extending into said hollowed ends for pivotally'supporting said armature, one of said members being itself hollow for the reception of a needle screw for securing a needle in said socket.

2. In an electric signal translating device, the combination of an armature including a pivot shaft hollowed out at its ends and having a socket therein, and bearing members having end engagement with said hollowed ends for pivotally supporting said armature, one of said members being itself hollow for the reception of a needle screw for securing a needle in said socket.

3. In an electric signal translating device, the combination of an armature including a pivot shaft, said shaft having a. bearing seat in one end thereof and being tapered at its other end to provide a bearing element, a hollow bearing sleeve in which said bearing element is mounted, and a solid bearing received in said seat whereby said armature is pivotally mounted.

4. In an electric signal translating device, the combination of an armature including a pivot shaft, said shaft having a conical bearing seat in one end thereof and being tapered at its other end to provide a bearing element, a hollow, conical bearing sleeve in which said bearing element is mounted, and a solid conical bearing received in said seat whereby said armature is pivotally mounted.

5. The invention set forth in claim 4 characterized in that said conical bearing sleeve is adjustable axially of said pivot shaft.

6. The invention set forth in claim 4 characterized in that said armature is provided with a socket, and characterized further by the addition of a needle screw received within said hollow bearing sleeve for securing a needle in said socket.

EMILE C. GUEDON'. 

